SVP-Pure®: Chlorate-Based Chlorine Dioxide Generator
Makes Controlling Odor Easy and Effective for U.S. Rendering
Plant
GOALS
Replace the existing chlorine dioxide (ClO2) generation and
feed system with a safer, simpler, and more reliable system.
SITE
A rendering plant in the western United States.
Summer 2003
HISTORY
In the mid-1990s, a rendering plant found itself located in an area experiencing a population boom.
Neighboring citizens complained regularly about the odor emitted from the plant. While the plant used
a masking agent for designed for odor control, the mixture of odors proved even more offensive. In
addition, two oil refineries, two feed mills, a food processing plant, and an animal food plant were also
located in the same vicinity—all of which contributed to the nuisance of foul odors. In 1997, the county
and state health departments began to take action to address the odor issues. About that same time,
the rendering plant made a transition from the masking agent to chlorine dioxide (ClO 2) as an
oxidizing agent for odor control. A traditional three-precursor ClO2 generation system using sodium
chlorite, hydrochloric acid, and sodium hypochlorite was installed and provided an immediate
reduction in the odors being emitted from the plant.
PROBLEM
The three-precursor ClO2 generation system did not have the capacity to maintain the oxidant level at
the necessary ORP set point—500 mV—especially during the high volume times that occurred in
conjunction with summer’s warmer temperatures.
The generation system required constant monitoring to ensure it was operating effectively. Operators
needed to check and adjust precursor rotometer settings every 15-30 minutes, and had to check for
air bubbles in lines. Eduction was used to deliver precursors into the generator and ClO 2 solution was
educted from the batch tank into the scrubber system. Multiple eduction processes resulted in very
poor dosage control. Most importantly, if the system failed, it was not easy for on-site personnel to fix
the problem.
The generation system relied on the use of a ClO2 batch tank in order to provide the necessary
conversion of precursors to ClO2. In order to accelerate the rate of ClO2 generation, excess acid and
sodium hypochlorite were used to speed production. The presence of the batch tank, containing
~1000 ppm ClO2 with excess HCl and NaOCl was a serious safety concern to plant operators.
Despite the use of excess acid and bleach, the ClO2 conversion only achieved 80% to 85%_far below
performance expectations, especially when managers factored in the amount of time and effort
operators invested in keeping the system operational.
Because of chlorine dioxide’s excellent ability to eliminate odor—and because citizen complaints had
dropped off dramatically following the implementation ClO 2 for odor control—the plant wanted to
continue using the molecule. However, they needed to upgrade to a larger, safer, simpler, and more
reliable ClO2 generation system.
SOLUTION
The rendering plant installed an SVP-Pure® ChlorateBased Chlorine Dioxide Generator. The two-chemical
ClO2 generation system uses Purate® (40% sodium
chlorate/10% hydrogen peroxide) and 78% sulfuric acid
solution. Advantages of the SVP Pure® system includes:
» Improved safety, simplicity, and reliability
» Savings on cost of chemical precursors
» Savings from improved ClO2 conversion efficiency
» Savings on operator service time
(automated feed control)
» Reduced citizen odor complaints
RESULTS
The plant staff were very pleased with the performance
and simplicity. During the first couple of months of the trial,
PureLine service technicians visited often to perform
standard changes to the ClO2 dosage settings in order to optimize the feed rate with the system flow
rate, and to train on-site personnel to troubleshoot problems. Once the feed rate was optimized, the
generator automatically provided the appropriate ClO 2 dose via flow-pacing software built into the
SVP-Pure® control system. Multiple safety interlocks and alarm features ensured safe and simple
operation, and the PureLine generator was much easier for on-site personnel to troubleshoot that the
previous three-precursor generator. Service visits decreased and were replaced with monthly system
check-ups and quarterly preventative maintenance—all performed by PureLine field technicians as
part of the contract.
Daily operator time for generator maintenance was reduced from constant monitoring to a routine,
once-a-day, five-minute system check, as well as periodic level check in the Purate and sulfuric acid
storage tanks. This new simplicity and improved reliability allowed plant personnel to focus on other
projects instead of monitoring previous old generator every 15-30 minutes. The plant manager was
pleased that “The generator just ran, and it ran well.”
Equally important, the SVP-Pure® system did not require a batch tank since SVP-Pure® technology
rapidly converts two precursors into a high purity ClO 2 solution at >95% efficiency. This ClO2 product
solution is then educted into the rendering scrubber water system using the generator’s automated
feed control system directed by ORP. Chlorine dioxide generation without the batch tank greatly
improved the safety and simplicity of the feed system while the SVP Pure automation system ensured
optimal feed control with minimal operator involvement.
In order to produce the same pounds per day of ClO2, the SVP-Pure® generator used 25% less
Purate than the amount of sodium chlorite required by the plant’s outdated system. Even if the dollarper-pound cost of Purate were the same as sodium chlorite, there would be a 25% reduction in the
cost for replacing sodium chlorite with Purate. In addition, replacement of hydrochloric acid and
sodium hypochlorite with sulfuric acid generated even greater cost savings.
Additional savings were realized due to improved ClO 2 conversion efficiency. While the old, threechemical generator operated at 80% to 85% efficiency, the SVP-Pure® system achieved 95% to 99%
efficiency.
The following table compares statistics that reflect the plant’s switch first from a “masking agent” to
the three-precursor ClO2 generator, and finally to the SVP-Pure® generator during the summer
months.
Odor Control Agent
Frequency of Complaints
“Masking agent”
1-5 per day
3-Precursor ClO2 Generator
1-2 per week
Pureline SVP-Pure ClO2 generator (unoptimized)
1 every two weeks
Pureline SVP-Pure ClO2 generator (optimised)
1-4 a year
CONCLUSION
While the plant’s initial transition from a “masking agent” to chlorine dioxide did result in better odor
control and a drop off in citizen complaints to from daily to weekly, complaints did persist because of
the three-precursor ClO2 generator’s poor reliability and insufficient capacity. By upgrading to the
SVP-Pure® ClO2 generator, odor complaints were dramatically reduced from weekly to quarterly.
The SVP-Pure® ClO2 generator was able to provided a dramatic improvement in safety and simplicity
over the old generator for several reasons—two versus three chemical precursors; elimination of the
ClO2 batch tank; a more reliable automated ClO2 feed system; and low-maintenance operation.
The SVP-Pure® ClO2 generator is more cost effective than the plant’s old three-precursor generation
system for several reasons—only two, not three, chemical precursors are needed; the system uses
25% less Purate® than sodium chlorite; and a 10% to 15% improvement in ClO 2 conversion
efficiency.